It has been considered that next generation radio communication system adopts MIMO (Multiple Input Multiple Output) system. It is known (see NPL 1) that MIMO system performs precoding based on channel information (CSI: Channel State Information) representing the state of a signal transmission path (a communication channel), which a transmitter applies to its transmission data, thus providing an improved frequency utilization efficiency compared to a frequency utilization efficiency which is produced without implementing precoding.
Generally speaking, FDD (Frequency Division Duplex) allows a receiver to receive channel information, wherein the following two methods (1), (2) (see NPL 2) are known as a method for precoding transmission data based on channel information.    (1) A channel response matrix received by a receiver is transmitted to a transmitter, which in turn performs precoding suited to the channel response matrix.    (2) A codebook having indexes regarding a plurality of precoders is shared between a receiver and a transmitter, wherein an index of a precoder suited to a channel response matrix received by the receiver is transmitted to the transmitter, which in turn utilizes a precoder specified by the index.